Pregnant rats will be ovariectomized and fetal pituitaries will be examined for ultrastructural changes. Pituitaries from neonatal rats treated with nafoxidine and antiestradiol serum will be studied for changes in basophil morphology. Fetal and neonatal pituitaries will be cultured with estrogen and then examined with the electron microscope to determine if this steroid has a direct effect. Pituitaries from estrogen deprived rats will be examined for histochemical and biochemical changes in enzyme activity. The effects of estrogen blockage on pituitary RNA synthesis will be determined by autoradiographic and biochemical techniques. Neonatal adrenals will be cultured and medium examined for estradiol by RIA. Adrenals will be incubated with various pituitary hormones to determine whether estrogen production by the adrenals is dependent upon pituitary factors. Growth hormone will be administered to nafoxidine treated rats. This experiment will attempt to reverse the physical changes brought about by nafoxidine.